It is faster and more efficient to crash all your ships together on your shipyards/drop-offs than wait for them to move. Being able to return a possible 4 ships per shipyard/drop-off per turn is a lot faster than just 1.

You only get halite for halite dropped off at a shipyard/dropoff. If you have 20 ships with 200 halite each at the end of the game, that’s 4000 halite you are wasting, and like the poster above said, it’s much easier at the end of the game to just crash your ships rather than waiting a turn for the one on the home to move because there is no penalty or bonuses for collisions or ship counts.